The goals of this proposal are to define the mechanisms by which human cells regulate the synthesis, secretion, degradation and activity of collagenase and, thus, of connective tissue metabolism in general. The modulating effect of the culture density of normal human fibroblast lines on collagenase expression has been established. We currently propose to examine the effects of other potential modulators of enzyme expression, such as pH of the growth medium, so that the optimum conditions can be established for assessing synthesis and secretion of collagenase in both normal and recessive dystrophic epidermolysis bullosa fibroblast cultures. A second major goal of this proposal is to evaluate fibroblast cultures from patients with recessive dystrophic epidermolysis bullosa for the existence of a mutant form of collagenase. Collagenase will be characterized from two mutant cell lines by comparing the thermal stability, cofactor kinetics, specific activity and immunologic properties of the putatively mutant enzymes with those from normal human fibroblasts.